Leaf surface specializations of birds and Arthropods in a Panamanian forest
Leaf surface specializations of birds and Arthropods in a Panamanian forest
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巴拿马森林中鸟类和节肢动物的叶面特化
作者：
R. Greenberg;J. Gradwohl
摘要大多数种类的巴拿马低地森林鸟类专门在树叶下表面时，狩猎树叶昆虫。少数种类的叶表面通才和叶上表面专家是杂食性拾穗者。我们估计，虽然超过90%的鸟类林下食虫是针对叶下表面，只有50%的冠层树叶食虫是针对叶的下侧。在低矮的林下植被中，我们发现70 - 80%的节肢动物在叶下。林下鸟类过度使用叶底可能是因为它们的可见度更高。据推测，不太熟练的食虫动物无法利用更大的有效密度的叶下昆虫，因为他们只能有效地攻击最近的叶片表面;这些最近的表面通常是叶顶从分支上的鸟栖息。另外，叶顶专家可能有特殊的觅食适应克服叶顶觅食的缺点。这些适应可能涉及攻击行为（Tachyphonus luctuosus）或搜索行为（Dacnis cayana）。达克尼斯经常利用叶片受损作为觅食的线索;这可能是第一次报道鸟类利用叶片受损来寻找昆虫。更多地使用叶上表面的冠层鸟类可能会受到四个因素的影响：更大的季节性的昆虫在冠层有利于杂食动物，这可能是效率较低的食虫动物;更多的昆虫在叶顶;较少的平面叶排列在冠层植物;或更大的可见度叶上表面的外壳的树叶的巨大的树木。基于更大数量的节肢动物叶底在旱季，更高丰度的小昆虫叶底，以及更大比例的昆虫叶顶在较冷的高海拔地区，我们建议，节肢动物更喜欢叶底在热带地区的生理，而不是捕食者回避的原因。
SummaryMost species of Panamanian lowland forest birds specialize on leaf undersurfaces when hunting foliage insects. The few species of leaf surface generalists and leaf upper surface specialists are omnivorous gleaners. We estimate that while over 90% of the avian understory insectivory is directed towards leaf undersurfaces, only 50% of canopy foliage insectivory is directed towards the undersides of leaves. In the low understory we found 70–80% of the arthropods on leaf undersides. The excess use of leaf-bottoms by understory birds may be a result of their greater visibility. It is hypothesized that less proficient insectivores are unable to take advantage of the greater effective density of underleaf insects because they can only efficiently attack the closest leaf surfaces; these closest surfaces will usually be the leaf tops from the branch on which the bird is perched. Alternatively, leaf-top specialists may have special foraging adaptations for overcoming the disadvantages of leaf-top foraging. These adaptations may involve attack behavior (Tachyphonus luctuosus) or searching behavior (Dacnis cayana). Dacnis often used leaf damage as a foraging cue; this may be the first report of a bird using leaf damage for searching for insects. The greater use of leaf upper surfaces by canopy birds may be influenced by four factors: greater seasonality of insects in the canopy favoring omnivores which may be less efficient insectivores; more insects on leaf tops; fewer planar leaf arrangements in canopy plants; or the greater visibility of leaf upper surfaces of the outer shell of foliage of massive trees. Based on the greater number of arthropods on leaf bottoms in the dry season, the higher abundance of smaller insects on leaf bottoms, as well as the greater proportion of insects on leaf tops at cooler higher elevations, we suggest that arthropods prefer leaf bottoms in tropical areas for physiological, not predator avoidance reasons.